The present invention relates to a wheel module which comprises a resiliently deformable inflation valve for a tire pressure monitoring system. More specifically, this wheel module is provided with a device for locking (or blocking in position) the position of an electronic casing on the valve.
Description of the Related Art
It is already known to provide motor vehicles with tire pressure monitoring systems. Such systems comprise:                a wheel module which is constituted by an electronic casing which is positioned on an inflation valve of a vehicle wheel, and        a central unit which is mounted on the frame of the vehicle.        
The electronic casing is conventionally provided with pressure, temperature and acceleration sensors, etc., which are capable of measuring the value of these parameters inside the tire. The electronic casing also comprises a unit for processing and analyzing the signals measured by these sensors. The measurements carried out are sent to the central unit via a wireless connection (generally a radio frequency connection).
The central unit receives the signals transmitted by each of the electronic casings. It analyzes and processes the signals received in order to inform the driver of any anomaly. The central unit is further capable of determining the position on the vehicle of each of the electronic casings from which it receives the signals.
Such tire pressure monitoring systems are well-known and will not be discussed in detail here.
The electronic casings which are fixed to each wheel of the vehicle are generally assembled on the inflation valve of these wheels and are arranged inside the covering of the tire. They are thus capable of measuring, for example, the pressure inside the tire.
There are two large types of inflation valves for tires.
A first type is constituted by metal inflation valves.
A second type is constituted by inflation valves of deformable resilient material (for example, rubber). This second type of valve is further called a “snap-in” type valve. These valves have the specific feature of having a body of resiliently deformable material whose diameter is greater than the hole of the wheel rim into which they are introduced. The positioning of these inflation valves is produced by forced introduction into this wheel rim hole. This positioning is made possible by the fact that the deformable body of the valve is stretched from resilient material. The temporary narrowing of the valve body obtained in this manner by this stretching allows it to be introduced into the hole of the wheel rim. After they have been positioned in the hole of the wheel rim, these valves return to their initial shape and the resilient material from which they are formed closes the hole of the wheel rim in a sealed manner. An inner conduit with respect to the valve allows air to be introduced into the tire in order to inflate it to the pressure recommended by the motor vehicle manufacturer.
These inflation valves therefore have a head of deformable material located at the inner side of the tire.
When a tire pressure monitoring system uses such a valve, it is necessary to fix an electronic casing on this valve head. To this end, there are numerous fixing systems, such as, for example, the one described in the patent application FR 2 918 315 to which reference may be made for further information.
It is thus known to provide the inner conduit of the inflation valve with a metal rod which extends toward the inner side of the tire and to which an electronic casing is fixed. The fixing of the electronic casing to this rod is further locked by a blocking element. The assembly constituted by the inflation valve and the electronic casing is called a wheel module below.
When it is desirable to mount a tire on a wheel rim which is provided with a wheel module, specific precautions must be complied with. In particular, the introduction of the assembly/disassembly tool of the tire must be carried out at a minimum distance from the location of the wheel module.
It has now been found that, during the assembly/disassembly of the tire, for various reasons, the assembly/disassembly instructions are not strictly complied with. This is the case both on production lines of the motor vehicle manufacturer and at workshops which are called upon to assemble/disassemble a tire. Consequently, the free edge of the tire is brought into contact with the wheel module and more specifically the electronic casing for monitoring the pressure of the tires. When the free edge of the tire moves above the electronic casing, a considerable force, in the order of 1000 N, is applied to the casing. In the case of a wheel module constituted by an electronic casing and a valve of the “snap-in” type, a blocking element which ensures that the casing is held in position with respect to the inflation valve is also subjected to this pressing force of the free edge of the tire. This pressing force has a tendency to open the blocking element, which brings about the disengagement of the electronic casing and the valve. Of course, such a disengagement renders the tire pressure monitoring inoperative.